An internal combustion engine typically includes at least one cylinder that receives a piston to form a combustion chamber. The piston is connected to a crankshaft such that a rotation of the crankshaft results in a corresponding reciprocating motion of the piston within the cylinder. Intake and exhaust valves associated with each combustion chamber are indirectly connected to the same crankshaft by way of a timing device such that a rotation of the crankshaft results in corresponding opening and closing movements of the intake and exhaust valves. Thus, the movements of engine valves and the motion of an associated piston, because of their connections to a common crankshaft, are synchronized.
The timing of the opening and closing movements of the intake and exhaust valves relative to the reciprocating motion of the piston affects performance of the engine. However, this timing of the engine is typically fixed according to a predicted general application of the engine. If operating in a manner other than that predicted, resulting performance of the engine can be less than desired.
In order to maximize the performance of the engine for a variety of applications, it can be beneficial to adjust the relative timing between the movements of the engine valves and the motion of the piston. This relative timing can be accomplished by way of a variable valve actuation device that selectively breaks the link between movement of the engine valves and rotation of the crankshaft. These variable valve actuation devices are typically electronically controlled, and often electronically actuated.
During operation of the engine described above, fuel may be injected into the combustion chamber and the injection synchronized with the reciprocating motion of the piston. For example, fuel may be injected as the piston nears a top-dead-center position in a compression stroke to allow for compression-ignited-combustion of the injected fuel. Alternatively, fuel may be injected as the piston begins the compression stroke heading toward a top-dead-center position for homogenous charge compression ignition operation. Fuel may also be injected as the piston is moving from a top-dead-center position towards a bottom-dead-center position during an expansion stroke for a late post injection to create a reducing atmosphere for aftertreatment regeneration. In order to accomplish these specific injection events, the engine is usually equipped with a fuel injector. The fuel injector is typically electronically controlled and often electronically actuated.
One example of an engine having an electronically controlled variable valve actuation device and an electronically controlled fuel injector is described in U.S. Pat. No. 6,651,618 (the '618 patent) issued to Coleman et al. on Nov. 25, 2003. The '618 patent describes an internal combustion engine having an intake valve assembly, a camshaft arranged to cyclically operate the intake valve assembly, and a variable intake valve closing mechanism arranged to interrupt the cyclical movement of the intake valve assembly. The internal combustion engine also includes a unit injector utilized to spray fuel into a cylinder of the internal combustion engine. The internal combustion engine further includes a controller electrically connected to the variable intake valve closing mechanism and the unit injector to power and control operation of the variable intake valve closing mechanism and the unit injector.
One problem associated with this type of arrangement may include power management. In particular, during certain operations of the internal combustion engine, such as at high engine speeds when multiple injections of fuel are required and when variable valve timing is simultaneously desired, the power supply of the controller may be insufficient to meet the electrical demands of both the fuel injector and the variable intake valve closing mechanism. In these situations, because the supply of power is insufficient to meet the power demands, the operation of both the fuel injector and the variable intake valve closing mechanism may be negatively affected, resulting in poor and/or unpredictable performance of the engine.
The power management system of the present disclosure solves one or more of the problems set forth above.